x86: no robust/pi futex for real i386 CPUs
Real i386 CPUs do not have cmpxchg instructions. Catch it before
crashing on an invalid opcode.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/futex.h b/include/asm-x86/futex.h
index cd9f894..c9952ea 100644
--- a/include/asm-x86/futex.h
+++ b/include/asm-x86/futex.h
@@ -102,6 +102,13 @@
static inline int
futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, int newval)
{
+
+#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_BSWAP)
+ /* Real i386 machines have no cmpxchg instruction */
+ if (boot_cpu_data.x86 == 3)
+ return -ENOSYS;
+#endif
+
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
return -EFAULT;